Protection Relays and Controls
Neutral-Grounding-Resistor Monitoring
SE-325 SERIES (PGM-8325)
Neutral-Grounding-Resistor Monitor
Description
The SE-325 Neutral-Grounding-Resistor Monitor is used on
resistance-grounded systems up to 25 kV to monitor the
integrity of the neutral-to-ground path and to detect ground
faults. It measures current and voltage in a transformer or
generator neutral-to-ground connection and continuity of the
neutral-grounding resistor (NGR). The SE-325 coordinates
these three measurements to detect a loose connection,
corrosion, ground fault, or NGR failure, and provides one alarm
or trip output contact.
Features & Benefits
FEATURES
Continuous NGR
monitoring
Ground-fault
Detection
Adjustable pickup
(0.5 - 4 A)
Adjustable time delay
(0.1 - 2 s)
Output contacts
Selectable contact
operating mode
BENEFITS
Detects resistor failure within seconds, reduces
transient-overvoltage risk, removes risk of ground-
fault-detection failure
Main or backup protection to detect a ground
fault anywhere on the monitored system
Select greatest sensitivity without
false operation
Adjustable trip delay allows system coordination
Form A output contact
Selectable fail-safe or non-fail-safe operating
modes allows connection to shunt or undervoltage
breaker coil or alarm system
Simplified Circuit Diagram
Accessories
CT
A
B
(Sensing Resistor)
ER SERIES
L1
L2
NGR
(NGR Monitor)
SE-325
SERIES
B
ER Series Sensing Resistor
Required interface between the power
system and the SE-325. Eliminates
hazardous voltage levels at the monitor.
CT200 Series Current Transformer
Required CT detects ground-fault current.
RK Series Remote Indication and Reset
Optional panel-mounted remote indication
and reset assemblies. Available in NEMA 1 or
NEMA 4 configurations.
A
Ordering Information
ORDERING NUMBER
CONTROL POWER
Specifications
IEEE Device Numbers
Input Voltage
Dimensions
GF Trip Level Settings
GF Trip Time Settings
RF Trip-Level Settings
Contact Operating Mode
Reset Button
Output Contacts
Approvals
Conformally coated
Warranty
Mounting
SE-325
SE-325D
SE-325E
120 Vac
120 Vac/Vdc
240 Vac
Consult manual online for additional ordering options.
ACCESSORIES
REQUIREMENT
CT200 Series
ER Series
SE-MRE-600
RK-325, RK-325I, RK-302
RK-13
NGRM-ENC
Required
Required
Optional
Optional
Optional
Optional
Ground Fault (50G/N, 51G/N),
Overvoltage (59N), Lockout Relay (86),
Checking Relay (3)
See ordering information
H
150 mm (5.9");
W
109 mm (4.3");
D
100 mm (4.0")
0.5-4.0 A
0.1-2.0 s
20-400 Vac (≤5 kV systems)
100-2,000 Vac (>5 kV systems)
Selectable fail-safe or non-fail-safe
Standard feature
Form A
CSA certified,
UL Listed (E340889),
C-Tick (Australian)
Standard feature
5 years
Surface
Rev: 4-B-102214
Based on Manual Rev:13-C-092314
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Littelfuse.com/se-325
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